snprintf (buf, sizeof(buf), "%f", _visible_speed);
node->add_property ("speed", buf);
node->add_property ("capture-alignment", enum_2_string (_alignment_choice));
snprintf (buf, sizeof(buf), "%f", _visible_speed);
node->add_property ("speed", buf);
node->add_property ("capture-alignment", enum_2_string (_alignment_choice));